The natural history of the various manifestations and complications of diabetes mellitus will be studied and evaluated in an Amerindian community. Various associated conditions and factors, including heredity, that may have a bearing on the frequency and severity of diabetes and/or its complications will also be investigated and selected findings will be contrasted with similar studies performed on other populations with different characteristics or environment. This will be done in connection with a prospective study of arthritis and rheumatism on the Amerindian population of the Gila River Indian Reservation. Examination will be carried out in a portable clinic building adjacent to the outpatient wing of the PHS Indian Hospital at Sacaton, Arizona, and will consist of a clinical interview, physical examination and special examinations to detect chronic vascular changes (soft tissue radiographs, photographs of the ocular fundi, electrocardiograms, etc.). In addition, glucose tolerance tests and other biochemical and serological tests will be performed.